On the other hand Wal-Mart has gone through a tremendous effort over the last couple of years to integrate environmental sustainability into not only its own practices but to force this into the supply chain."

VOA: standard.2010.01.23

There's the hard sphere. It wants to collide against the wall to create a force on the wall, and I have a couple of the hard spheres that are nearby, right, and in the absence of any interactions, I get a certain pressure.

给墙一个作用力,现在它的附近，还有许多小球,没有相互作用时,它将直接冲向这面墙。

麻省理工公开课 - 热力学与动力学课程节选